Multi channel communications for vehicular radio communications for bi-directional communications with local wireless device

ABSTRACT

A vehicular radio communications system establishes a bi-directional digital radio communications link between a local wireless communication device inside a moving vehicle and a sequence of radio transceivers in a wireless network. The local device operates in a plurality of different device frequency bands and the external transceivers operate in a plurality of different network frequency bands. Some or all of the device frequency bands are the same as some or all of the network frequency bands. The system comprises a set of one or more external radio antennas operating in an external downlink and an external uplink using a network frequency band and a set of one or more local radio antennas operating in a local downlink and a local uplink using a local frequency band different from the network band.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to United Kingdom Patent ApplicationNo. 1517560.7 filed Oct. 5, 2015, and entitled “MULTI CHANNELCOMMUNICATIONS,” which is herein incorporated by reference.

BACKGROUND

The present disclosure relates to vehicular radio communications systemsfor establishing a bi-directional digital radio communications linkbetween a local wireless communication device inside a moving vehicleand a sequence of radio transceivers in a wireless network external ofsaid vehicle.

Cars currently can have multiple external antennas for various differentpurposes, for example: receiving and sending LTE (long term evolution)cellular transmission as in the 4G mobile communications standard;receiving digital audio broadcasts (DAB) or other digital audiobroadcast, such as HD Radio (Reg. TM); and receiving and sending data ina wide area network (WLAN), for example by using WiFi (Reg. TM).

It is known to use multiple external antennas, and two is usual, whenreceiving so that frequencies can be switched when coming into range ofa better signal. An additional “sniffing” antenna can be used to monitorsignal strength across a range of frequencies.

Cars can have multiple internal antennas for retransmitting the signalsinside the vehicle. Clearly, the same frequencies cannot be usedsimultaneously both inside and outside the vehicle or else there will beinterference. Different frequencies are therefore used internal to thevehicle.

Some types of electronic component used with in-vehicle communicationssystem are relatively expensive. The simplest, but most expensive, wayof providing receive/transmit paths both inside and outside the vehicleis to use many separate receive RF paths and many separate RF transmitpaths, both for inside and outside the vehicle. The conventionalapproach is for each antenna to have its own, separate RF circuitrycovering all the bands and frequencies for that antenna. However, whenthe RF paths are all separate, there can be the need for many of therelatively expensive RF power amplifiers, not to mention duplication ofless expensive components.

It would be desirable to have a solution which is “worldwide” so thatthe same “box” can be supplied to an auto manufacturer regardless ofwhere in the world the vehicle will be sold. LTE 4G mobile is aparticular problem as there are currently 45 bands globally. Each bandcovers a spread of frequencies. There is one cluster of LTE bandsbetween 700 MHz and 950 MHz, and another cluster about 1.4 GHZ and about2.7 GHZ and a few at between about 3.4 GHz and 3.8 GHz. When there is asingle antenna, 90 RF paths (receive and transmit) would be neededexternal to the vehicle and 90 RF paths internal to the vehicle in orderto provide functionality across all 45 bands. In practice, differentregions of the world have different combinations of bands, so not allpaths would need to be implemented if a vehicle is to be used in justone of these regions. However, as there is a desire to standardisevehicular components worldwide, as far as possible, in principle thiswould require all equipment implementing all 90 paths, both externallyand internally to the vehicle.

With two antennas both external and internal, these numbers double. Tothis can be added the requirement to provide for WiFi communication withadditional antennas and circuitry. There are currently two WiFi bands,but this will probably expand to 5 to 7 in a few years.

SUMMARY

According to the aspects disclosed herein, there is provided a vehicularradio communications system for establishing a bi-directional digitalradio communications link between a local wireless communication deviceinside a moving vehicle and a sequence of radio transceivers in awireless network external of said vehicle, said local device operatingin any one of a plurality of different device frequency bands and saidradio transceivers each operating in any one of a plurality of differentnetwork frequency bands such that different radio transceivers havedifferent network frequency bands of operation, some or all of saiddevice frequency bands being the same as some or all of said networkfrequency bands, wherein the vehicular radio communications systemcomprises:

-   -   a set of one or more external radio antennas for radio        communication with said network, each external radio antenna        being configured for operation in any of said network frequency        bands and each being operable, in use, to receive and transmit        radio signals in, respectively, an external downlink and an        external uplink thereby providing, in use, an external radio        communications link using said network frequency band of        operation, said network frequency band of operation changing in        accordance with said sequence of radio transceivers as said        vehicle moves;    -   a set of one or more local radio antennas for radio        communication with said local device, each local radio antenna        being configured for operation in any of said device frequency        bands and each being operable, in use, to receive and transmit        radio signals in, respectively, a local downlink and a local        uplink thereby providing, in use, a local radio communications        link using said device frequency band of operation, said device        frequency band of operation changing in accordance with said        changes in said network frequency band of operation so as to be        different from said network frequency band of operation;    -   a bi-directional processor configured to process signals        received from the local downlink for transmission in the        external uplink and to process signals received from the        external downlink for transmission in the local uplink;    -   a plurality of selectable radio-frequency interfaces, each one        of said radio-frequency interfaces being configured for        operation in a different frequency band and comprising a duplex        processor interface and a duplex antenna interface, said duplex        processor interface being selectively connectable to said        processor and said duplex antenna interface being selectively        connectable to any of said radio antennas of both of said sets        of antennas, and said plurality of radio-frequency interfaces        comprises: (i) a first selected radio-frequency interface        comprising a first duplex processor interface and a first duplex        antenna interface connected respectively to said processor and        to a first radio antenna, said first radio antenna being in said        set of external radio antennas; and (ii) a second selected        radio-frequency interface comprising a second duplex processor        interface and a second duplex antenna interface connected        respectively to said processor and to a second radio antenna,        said second radio antenna being in said set of local radio        antennas;    -   a switching system configured to switch any of said selectable        radio-frequency interfaces into connection between said        processor and the corresponding radio antenna to maintain the        external radio communications link when the network frequency        band of operation changes and to maintain the local radio        communications link when the device frequency band of operation        changes;    -   a control system, the control system being connected to the        switching system and being configured to select which of said        selectable radio-frequency interfaces will be switched by the        switching system so that the device frequency band of operation        continues to be different from the network frequency band of        operation when there is to be a change in the network frequency        band of operation, whereby the first selected radio-frequency        interface is one that is configured for duplex operation at the        network frequency band of operation and the second selected        radio-frequency interface is one that is configured for duplex        operation at the device frequency band of operation, said        bi-directional digital radio communications link, in use,        thereby being provided through said first and second        radio-frequency interfaces and said radio signal processor as        said external and local radio communications links are        maintained by the switching system under the control of the        control system.

Although the change in the network frequency band of operation will, inmost cases, be due to movement of the vehicle relative to the externaltransceivers, the change may sometimes be necessitated by other factors,for example external factors such as weather, radio interference, and achange may also be required on account of the cost or quality of thedata service.

The vehicular radio communications system may comprise at least tworadio antennas in said set of external radio antennas. This may,alternatively or additionally, comprise at least two radio antennas insaid set of internal radio antennas.

The plurality of radio-frequency interfaces may comprises: (i) a thirdselected radio-frequency interface comprising a third duplex processorinterface and a third duplex antenna interface connected respectively tosaid processor and to a third radio antenna, said third radio antennabeing in said set of external radio antennas; and (ii) a fourth selectedradio-frequency interface comprising a fourth duplex processor interfaceand a fourth duplex antenna interface connected respectively to saidprocessor and to a fourth radio antenna, said fourth radio antenna beingin said set of local radio antennas.

The duplex operation will in general comprise a port for receiving fromthe antenna a downlink radio signal and providing to the antenna anuplink radio signal.

Each antenna may have has a frequency response that is optimised for aplurality of specific frequency band. Therefore, there may, in eachantenna set, be just one antenna covering all frequency bands.

The duplexer may be a half duplexer, in which either the uplinkamplifier or the downlink amplifier is silenced in order to avoidcross-talk between the uplink and downlink amplifiers. However, it willmost usually be the case that the duplexer is a full duplexer to permitthe radio transceiver amplifier circuit to both receive and transmit atthe same time, as is the case, for example, in mobile telephony.

Each of the selectable radio-frequency interfaces may be configured forfixed operation in a single frequency band.

In one preferred embodiment, the frequency response of each radiofrequency interface is fixed, and the control system switches theselectable radio-frequency interfaces into connection between saidprocessor and the corresponding radio antenna so that the selectedradio-frequency interface matches the frequency response of eachinterface to the required frequency band to be used by using theswitching system to switch the duplex input/output of each interface tothe appropriate or optimal antenna for the required frequency band ineither one of the first or second sets of antennas. This aspect of theinvention therefore makes use of the fact that since the frequency bandsof operation in the external and local radio communications links mustbe different in order to avoid radio interference, it is possible tohalve the number of required interfaces if there is just one interfacefor each required band and if the switching system is capable ofconnecting each interface, as required to either the first set ofantennas for the external radio communications link, or the second setof antennas for the local radio communications link. Any of the transmitpaths and the receive paths not being used in one of the interfaces arethen available for use in the other interface.

In one embodiment, each of the radio-frequency interfaces is a tuneablemulti-frequency interface configured for frequency tuneable operation ina plurality of different frequencies bands.

The control system may be operatively connected to each tuneablemulti-frequency interface, in which case the control system controls thefrequency response of each interface to the required frequency band ofoperation.

In this preferred embodiment each of the first and secondradio-frequency interfaces is a frequency-tuneable interface capable ofbeing tuned or adjusted to operate at any one of a plurality ofdifferent operating frequency bands. In this case, the control system isoperatively connected to each tuneable multi-frequency interface, andthe control system matches the frequency response of each interface tothe required frequency band to be used by changing the operatingfrequency band of each interface.

The vehicular radio communications system may therefore comprise afrequency adjustment system for adjusting the operational frequency offilters and/or amplifiers of said interface and the control system isconnected to each of said frequency adjustment systems and is configuredto coordinate the adjustment of said operational frequencies of said offilters and/or amplifiers in accordance with said changes in saidfrequency bands to be used.

The control system may be operable, in use, to change the frequencyresponse of a receiver amplifier and/or a transmitter amplifier withinthe radio-frequency interface to match said changes in the networkfrequency band of operation.

The control system may be operable, in use, to change the frequencyresponse of at least one frequency filter circuit selectably linkable tothe receiver amplifier and/or at least one selectable frequency filtercircuit selectably linkable to the transmitter amplifier, the controlsystem being operable, in use, to select which of these frequency filtercircuits is linked to the amplifiers in order to change the frequencyresponse of the receiver amplifier and/or the transmitter amplifier.

Each radio-frequency interface may comprise between the duplex processorinterface and the duplex antenna interface a transceiver system, thetransceiver system comprising a transceiver amplifier circuit, saidcircuit comprising a receive path and a transmit path, the receive pathincluding a receiver amplifier being configured to amplify a downlinkradio signal received from the duplex antenna interface and to providesaid amplified signal to the duplex processor interface. The transmitpath includes a transmitter amplifier that is configured to amplify theuplink radio signal received from the duplex processor interface and toprovide the amplified signal to the duplex antenna interface.

In a preferred embodiment, the switching system comprises, between saidradio frequency interfaces and the bi-directional processor, a processormultiplexer.

The processor multiplexer may then be connected to the duplex processorinterface.

The processor multiplexer is preferably connected to a coder/decoderinterface of the bi-directional processor.

In a preferred embodiment, the switching system comprises, between saidradio frequency interfaces and the sets of antennas, an antennamultiplexer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, andwith reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of a prior art vehicular radiocommunications system for establishing a bi-directional digital radiocommunications link between a local wireless communication device insidea moving vehicle and a sequence of radio transceivers in a wirelessnetwork external of said vehicle, in which each radio frequency (RF)communications path is through a multiplexed RF interface operable in aplurality of different bands;

FIG. 2 is a schematic circuit diagram showing the components of one ofthe multiplexed RF interfaces, having two selectable radio-frequencyinterfaces, each being configured for operation in a different frequencyband;

FIG. 3 is a schematic representation of a vehicular radio communicationssystem according to a preferred embodiment of the invention, forestablishing a bi-directional digital radio communications link betweena local wireless communication device inside a vehicle and a sequence ofradio transceivers in a wireless network external of said vehicle, inwhich a plurality of radio-frequency interfaces is multiplexed andavailable for use in both internal and external communications pathswithin the vehicle under the control of a system controller; and

FIG. 4 shows a variant of the radio-frequency interfaces of FIG. 3, inwhich the frequency response of each of the radio-frequency interfacesis tuneable under the control of the system controller.

DETAILED DESCRIPTION

FIG. 1 of the drawings shows a known vehicular radio communicationssystem 1 for establishing a bi-directional radio digital communicationslink between a two local wireless communication devices D₁ and D₂ 2, 4inside a moving vehicle 6 and two corresponding wireless networks 3, 5external of the vehicle. In this example, a first one of the devices D₁is a mobile telephone 2 in communication through a first antenna 11 witha first mast t2 7 in a cellular telephone network 3 and the second oneof the devices is a tablet computer in communication through a secondantenna 12 with a first WiFi (Reg. TM) hotspot T2 9 in a WLAN network 5.

Each of the digital communications links may comprise one or moreadditional antennas and in this example the cellular communications linkhas a third antenna 13 and the WLAN communications link has a fourthantenna 14.

In this example, both communications links use multiple-input andmultiple-output, or MIMO communications standards, for example usinglong term evolution (LTE) (the cellular 4G standard) for the cellulartelephone network 3. The particular type of digital communicationsstandard used is not a particular feature of the invention to bedescribed below, and is given purely as an example.

As the vehicle moves relative to the external wireless networks 3, 5having a plurality of transceivers 7, 7′, 17, 9, 9′, 19 it becomesnecessary to switch to a new network antenna 17, 19 as signal strengthfrom the current antenna 7, 9 drops, and the next antenna will, ingeneral, use a different frequency band than the current antenna. When aswitch is to be made, this may be accomplished using the same vehicleexternal antenna 11, 12 or another vehicle external antenna 13, 14. Theillustrated example shows the case where a different vehicle antenna isused when frequencies are to be changed. If the same vehicle antenna isto be used, then the system will require additional multiplexing stageby which the same antenna can be switched between different interfaces.

In this example, in additional to the two pairs of external digitalcommunications antennas 11, 13 and, 12, 14, there are also twocorresponding pairs of internal or local digital communications antennas21, 23 and, 22, 24 within the vehicle itself, each pair being for localradio communication with the two devices 2, 4.

In this simplified example, only one antenna of each pair could be usedat any one time. This is because this example provides just two radiofrequency (RF) bands for each of the two radio digital communicationslinks. Each RF band employs two different frequencies: one for transmit(the “high band” or HB) and one for receive (the low band or LB). Anexternal radio link 31, 32 in use must therefore use a different band toan internal radio communications link 41, 42 in use. This differencemust be maintained when radio frequencies change so that the bands usedin the next external radio links 33, 34 continue to employ differentbands to those to be used in the next internal radio communicationslinks 43, 44.

As can be seen from FIG. 1, with two bands for each of two differentradio communications networks, 3, 5, there is the need for eightdifferent RF interfaces 51-58 each of which has a transmit, or uplinkportion and a receive, or downlink portion, from the respective internaland external antennas. As is known in the art, each receive/transmitinterface will have an antenna interface in the form of a duplexprocessor for separating the receive and transmit signals.

Signals are passed between external RF interfaces 51-54 and internal RFinterfaces through a bi-directional signal processor system 50. In thisdescription, this system is referred to as a base band processor 50.This bi-directional signal processor system includes a main processor59, and interface stages 61-64 to which of the external RF interfaces51-58 is connected. The interface stages include LTE base band decodersand coders 61, 63 for cellular communication and external and internalWLAN decoders and coders 62, 64 for WLAN communication.

Optionally, there may be additional antennas, such as a sniffing antenna15 and a GPS antenna 16. The sniffing antenna 15 is connected to aninterface 65, which may be built into the application processor 59, andis used by the application processor to measure signal strengths fromthe antennas 7′, 7, 17 in the cellular telephone network 3, so that theapplication processor can coordinate the switching of communicationbands as different external signal strengths increase or diminish. TheGPS antenna 16 is connected to a GPS receiver 66 which may providesignals to different devices inside the vehicle, for example anavigation system (not illustrated) and the application processor 59.

The main processor in this example is referred to as applicationprocessor 59. Although the term “base band processor” is sometimes usedspecifically for this main processor, in this description the term “baseband processor” is encompasses both the main processor and any necessaryassociated interface stages 61-64 for connection to the RF interfaces51-58.

In practice, more than just two different bands will be required in eachnational market, for example, between about 8 and 12 bands. In thesystem of FIG. 1, this would require between about 16 and 24bi-directional RF interfaces. To provide a system that could beinstalled in vehicles worldwide it would be necessary to providecoverage of 45 bands in the MIMO-LTE cellular 4G standard, and this inturn would require 90 bi-directional RF interfaces.

In FIG. 1, the eight RF interfaces 51-58 are illustrated as grouped intofour RF interface blocks, labelled as 40A, 40B, 40C, 40D. It will beappreciated, however, that the RF interfaces may all be provided in asingle integrated circuit chip.

Although the internal and external receive/transmit RF powers are verydifferent it is possible to use the same circuit components in each ofthe RF interfaces, as long as the circuitry has appropriate gaincontrol. FIG. 2 shows one conventional arrangement of circuit componentsfor one of the illustrated RF interface blocks 40A, and also how thesecomponents are connected to the base band processor 50 and to two of theantennas 11, 13. The components are grouped into two transceivers eachof which has a transmit path 20 and a receive path 30, these pathsextending between an input multiplexer 70, which is at the base bandprocessor end of each path 20, 30, and a duplexer 80, which is at theantenna end of each path. The input multiplexer 70 is common to all thereceive and transmit paths 20, 30. The transmit path 20 receives abalanced differential digital signal 67 from the input multiplexer whichpasses through a balun 68 and is converted into a unbalanced singleended signal 69. The single ended signal is filtered by a saw (surfaceacoustic wave) filter 71, and the filtered signal 72 is then amplifiedby an RF power amplifier 73. The output 74 from the power amplifier isfiltered by a low pass filter 75, and the filtered output 76 is thenprovided to a transmit input TX 77 of the duplexer 80.

Saw filters are electromechanical devices commonly used in radiofrequency applications. Electrical signals are converted to a mechanicalwave in a device constructed of a piezoelectric crystal or ceramic; thiswave is delayed as it propagates across the device, before beingconverted back to an electrical signal by further electrodes. Thedelayed outputs are recombined to produce a direct analog implementationof a finite impulse response filter. This hybrid filtering technique isalso found in an analog sampled filter. SAW filters are limited tofrequencies up to 3 GHz.

As an alternative to saw filters, it is possible to use baw (bulkacoustic wave) filters, which are also electromechanical devices. Bawfilters can implement ladder or lattice filters. Baw filters typicallyoperate at frequencies from around 2 GHz to around 16 GHz, and may besmaller or thinner than equivalent saw filters.

Each duplexer 80 has an RF transceiver input/output RF 81 that isconnected to an output multiplexer 82 which is configured to provide andreceive signals 83 from one of the antennas 11, 13 at a time.

On the receive path 30, a receive output RX 84 from the duplexer 80 isprovided to a low noise RF amplifier 85. The output 86 from the lownoise amplifier is filtered by a saw filter 87, and the filtered signal88, which is an unbalanced signal-ended signal, is then provided to abalun 89 and is converted into a balanced digital signal 99 and thenprovided to the input multiplexer 70.

The input multiplexer 70 receives and provides digital signals from atransceiver interface 90. These signals include balanced digital signalsfor transmit data TX_P and TX_N 91 and receive data RX_P and RX_N 92.

The transceiver interface 90 is connected by a data bus 93 to the baseband processor 50. Data signals 94, 95 between the transceiver and baseband processor 50 include data sent to and received from the antenna 11,13 that is in use, as well as control signals to the input multiplexer70 to select which one of the paired transmitter and receive paths 20,30 will be used. The control signals also control a digital-to-analogconverter (DAC) output 96 from the transceiver interface 90 which ispassed as an analog control signal 97 by the multiplexer to the RF poweramplifier 73 that is in use in order to control the gain of theamplifier and hence strength of the transmit signal 83 from the antenna11, 13 that is in use.

Some of the components of the transceiver circuitry, in particular thehigh power and low noise RF amplifies 73, 85, are relatively expensive,which may make it commercially impractical to provide hardware that canused anywhere in the world or with multiple different type of externalnetwork 3, 5.

A preferred embodiment of the invention, as illustrated in FIG. 3,therefore provides a vehicular radio communications system 101 whichmakes more efficient use of radio-frequency interfaces. In FIG. 3,features which are the same as those of FIG. 1 are indicated using thesame reference numerals, and for the sake of clarity may not thereforebe fully described again.

The vehicular radio communications system 101 includes a bi-directionalprocessor 150, which is in this example a base band processor,configured to process signals received from a local downlink from one ormore in-vehicle devices D1, D2 2, 4 for transmission in an externaluplink and to process signals received from an external downlink fortransmission in the local uplink.

The system 101 includes a plurality of selectable radio-frequency (RF)interfaces 151-154, each one of which is configured for operation in adifferent frequency band. FIG. 4 shows an example of one of the RFinterfaces 151-154, which preferably all use the same components andconstruction.

Each RF interface 151 has a duplex processor interface 190, similar tothe transceiver 90 described above, and a duplex antenna interface 180,similar to the duplexer 80 described above.

The duplex processor interface 190 of each RF interface is selectivelyconnectable to the bi-directional processor 150 through a firstmultiplexer 45, or “processor multiplexer” MX_(P). The duplex antennainterface 180 is selectively connectable to both internal and externalradio antennas through a second multiplexer 46, or “antenna multiplexer”MX_(A).

Since it may be that radio antennas for communication with differentexternal networks 3, 5 are optimised for particular powers or frequencybands, it may still however, be the case that there will be more thanone set of external antennas and more than one set of internal antennas,as illustrated in FIG. 3. In this case, when there are RF interfaces formore than one type of external network, the interfaces for one type ofnetwork will not be selectable by the antenna multiplexer for connectionto an internal or external antenna for another type of network.

There may be any practical number of RF interfaces, but in theillustrated examples there is, for each of the two different externalnetworks 3, 5 a first selected radio-frequency interface 151, 153comprising a first duplex processor interface 190 and a first duplexantenna interface 180 connected respectively to the bi-directionalprocessor 150 and to a first radio antenna 11, 12 which is an externalradio antennas. For each of the two different external networks 3, 5there is also a second selected radio-frequency interface 152, 154comprising a second duplex processor interface 190 and a second duplexantenna interface 180 connected respectively to the bi-directionalprocessor 150 and to a second radio antenna 21, 22, which is an internalor local radio antenna.

The processor and antenna multiplexers 45, 46 provide a switching systemconfigured to switch any of the selectable radio-frequency interfaces151,152 or 153,154 into connection between the processor 150 and thecorresponding radio antenna 11,12,21,23 or 12,14,22,24 to maintain theexternal radio communications link when the network frequency band ofoperation changes and to maintain the local radio communications linkwhen the local, device frequency band of operation changes.

To coordinate this, there is also a control system, referred to in FIG.3 as a “controller” 47. Although the controller is illustrated as beinga separate component from the bi-directional processor 150, thecontroller may be physically integrated on the same chip with theprocessor 150.

The control system 47 is connected 48 to the switching system 45, 46 andis configured to select which of the selectable RF interfaces 151-154will be switched by the switching system so that the local or devicefrequency band of operation continues to be different from the externalor network frequency band of operation when there is to be a change inthe network frequency band of operation, for example owing to movementof the vehicle 106 relative to the external networks 3, 5.

The first selected radio-frequency interface is therefore one that isconfigured for duplex operation at the network frequency band ofoperation and the second selected radio-frequency interface is one thatis configured for duplex operation at the device frequency band ofoperation, the bi-directional digital radio communications link, in use,thereby being provided through the first and second radio-frequencyinterfaces and the radio signal processor as the external and localradio communications links are maintained by the switching system underthe control of the control system as the vehicle moves and the networkfrequency bands of operation change in accordance with the particularsequence of radio transceivers t1, t2, t3 or T1, T2, T3.

In this way, an initial uplink and downlink once established for eachone of the external networks is maintained without interference betweenany of the radio transmissions inside or outside the vehicle. Byemploying the same RF interfaces with both internal and externalantennas, needless duplication of RF interfaces is avoided.

The RF interfaces 151-154 may each be optimised for receive and transmitoperation in a single band of operation, for example as illustrated forthe receive and transmit paths 20, 30 of FIG. 2. FIG. 4 shows anoptional feature of the invention, in which each receive and transmitpath 120, 130 is frequency tuneable. In this case, the control system 47is connected to switchable components within each RF interface 151-154.In this example, these switchable components are: a plurality ofrf-switchable balun bands 268 within a transmit path balun 168; aplurality of rf-switchable saw filter bands 271 within a transmit pathsaw filter 171; a plurality of rf-switchable power amplifier bands 273within a wide band RF transmit amplifier 173;

a plurality of rf-switchable low noise amplifier bands 285 within a lownoise RF receive amplifier 185; a plurality of rf-switchable saw filterbands 285 within a receive path saw filter 185; and a plurality ofrf-switchable balun bands 289 within a receive path balun 189.

Other components common to the transmit and receive paths 120, 130, suchas the duplexer 180, may also require frequency tuning, and in thisexample, there is also a plurality of rf-switchable duplexer bands 280within the duplexer 180 connected to the control system 47.

The particular choice of switchable components for controlling thefrequency response of active or passive circuit components will, ofcourse, depend on the particular design of the components used in thetransmit and receive paths.

The components of each RF interface 151-154 provide a single transceiverhaving a transmit path 120 and a receive path 130. These paths extendbetween the duplex processor interface 190, which is at the processormultiplexer end of each path 120, 130, and an antenna duplexer 180,which is at the antenna multiplexer end of each path. The transmit path120 receives a balanced differential digital signal 167 from the duplexprocessor interface 190 which passes through a balun 168 and isconverted into a unbalanced single ended signal 169. The single endedsignal is filtered by a saw filter 171, and the filtered signal 172 isthen amplified by an RF wide band power amplifier 173. The output 174from the power amplifier is provided to a transmit input TX 177 of theantenna duplexer 180.

Each antenna duplexer 180 has an RF transceiver input/output RF 181 thatis connected to the antenna multiplexer 46 which is configured toprovide and receive signals 183 to and from a selected one of theexternal antennas 11-14 or a selected one of the local antennas 21-24.

On the receive path 130, a receive output RX 184 from the duplexer 180is provided to the low noise RF amplifier 185. The output 186 from thelow noise amplifier is filtered by a saw filter 187, and the filteredsignal 188, which is an unbalanced signal-ended signal, is then providedto a balun 189 and is converted into a balanced digital signal 199 andthen provided to the duplex processor interface 190.

The transceiver interface 190 is connected by a data bus 193 to thebi-directional base band processor 150 through the processor multiplexer45. Data signals 194, 195 conveyed through the multiplexer 45 betweenthe transceiver and processor 150 include data sent to and received fromthe antenna 11-14 or 21-24 that is in use, as well as control signalsincluding those for a digital-to-analog (DAC) output 196 from thetransceiver interface 190 which is passed as an analog control signaldirectly to the RF wide band power amplifier 173 in use in order tocontrol the gain of the amplifier and hence strength of the transmitsignal 183 from the antenna 11-14 or 21-24 that is in use.

The duplex processor interface 190 also receives and provides balanceddigital signals for transmit data TX_P and TX_N 191 and receive dataRX_P and RX_N 192.

By using the frequency tuneable RF interfaces, it is possible to make afurther reduction in the number of RF interfaces needed to cover a largenumber of possible different operating bands. Because the system employsthe processor multiplexer and the antenna multiplexer, it is notnecessary that each RF interface is tuneable for all possible bands. Themain reason for this is that the bi-directional processor will, in mostcases, be free to determine which bands will be used inside the vehicle,within the constraint that the local bands must not be the same as anyexternal bands in use. When there are at least four bands to cover, itbecomes sensible to provide frequency tuning capability for at leastsome of the RF interfaces. For example, when there are four bands tocover, there can be two RF interfaces with: (i) one being tuneableacross each three bands none of which is the same as that for the otherRF interface; or (ii) both being tuneable across two different bands,none of the bands being the same. The possible reduction in expensivecomponents such as RF amplifiers is then even greater when a very largenumber of bands are to be covered.

In the embodiments of the invention described above, the local wirelesscommunication device is inside a passenger compartment of a road goingmotor vehicle, here a car, for conveying at least one passenger. Theelectronic device may be a hand-held device, for example a personalcommunication device, for example a mobile phone, a tablet or laptopcomputer or any other type of hand-held device. The invention is,however applicable to other types of electronic device, including thosepermanently connected to the vehicle as part of the passengercompartment or instrument display and also to different types of vehiclehaving an internal compartment for conveying at least one passenger.

The local wireless communication device may, for example, be part of anelectronic device such as a vehicle engine management system, an in-caraudio entertainment system, or a built-in mobile telephony device. Theremay be a single wireless communication device inside the vehicle,however, the invention is applicable to cases where there is more thanone such device, each device being assigned its own identifier such asan Internet Protocol (IP) address.

The disclosure described above maintains separation between frequencybands in use for local and external radio communication, therebyavoiding radio interference as the vehicle moves into and out of radiocommunication with different external radio transceivers. At the sametime, the invention permits a simplification of the system architectureand switching control scheme for a given number of required number RFpaths. The number of components can be reduced accordingly, thusreducing system cost and packaging space. The invention thereforeprovides a convenient vehicular radio communications system thatprovides one or more bi-directional digital radio communications linksbetween a local wireless communication device inside a moving vehicleand one or more corresponding sequences of radio transceivers inexternal wireless networks.

The invention claimed is:
 1. A vehicular radio communications system forestablishing a bi-directional digital radio communications link betweena local wireless communication device inside a moving vehicle and asequence of radio transceivers in a wireless network external of saidvehicle, said local device operating in any one of a plurality ofdifferent device frequency bands and said radio transceivers eachoperating in any one of a plurality of different network frequency bandssuch that different radio transceivers have different network frequencybands of operation, some or all of said device frequency bands being thesame as some or all of said network frequency bands, wherein thevehicular radio communications system comprises: a set of one or moreexternal radio antennas for radio communication with said network, eachexternal radio antenna being configured for operation in any of saidnetwork frequency bands and each being operable, to receive and transmitradio signals in, respectively, an external downlink and an externaluplink thereby providing an external radio communications link based onsaid network frequency band of operation, said network frequency band ofoperation changing in accordance with said sequence of radiotransceivers as said vehicle moves; a set of one or more local radioantennas for radio communication with said local device, each localradio antenna being configured for operation in any of said devicefrequency bands and each being operable, in use, to receive and transmitradio signals in, respectively, a local downlink and a local uplinkthereby providing, in use, a local radio communications link using saiddevice frequency band of operation, said device frequency band ofoperation changing in accordance with said changes in said networkfrequency band of operation so as to be different from said networkfrequency band of operation; a bi-directional processor configured toprocess signals received from the local downlink for transmission in theexternal uplink and to process signals received from the externaldownlink for transmission in the local uplink; a plurality of selectableradio-frequency interfaces, each one of said radio-frequency interfacesbeing configured for operation in a different frequency band andcomprising a duplex processor interface and a duplex antenna interface,said duplex processor interface being selectively connectable to saidprocessor and said duplex antenna interface being selectivelyconnectable to any of said radio antennas of both of said sets ofantennas, and said plurality of radio-frequency interfaces comprises:(i) a first selected radio-frequency interface comprising a first duplexprocessor interface and a first duplex antenna interface connectedrespectively to said processor and to a first radio antenna, said firstradio antenna being in said set of external radio antennas; and (ii) asecond selected radio-frequency interface comprising a second duplexprocessor interface and a second duplex antenna interface connectedrespectively to said processor and to a second radio antenna, saidsecond radio antenna being in said set of local radio antennas; aswitching system configured to switch any of said selectableradio-frequency interfaces into connection between said processor andthe corresponding radio antenna to maintain the external radiocommunications link when the network frequency band of operation changesand to maintain the local radio communications link when the devicefrequency band of operation changes; a control system, the controlsystem being connected to the switching system and being configured toselect which of said selectable radio-frequency interfaces will beswitched by the switching system so that the device frequency band ofoperation continues to be different from the network frequency band ofoperation when there is to be a change in the network frequency band ofoperation, whereby the first selected radio-frequency interface is onethat is configured for duplex operation at the network frequency band ofoperation and the second selected radio-frequency interface is one thatis configured for duplex operation at the device frequency band ofoperation, said bi-directional digital radio communications link, inuse, thereby being provided through said first and secondradio-frequency interfaces and said bi-directional processor as saidexternal and local radio communications links are maintained by theswitching system under the control of the control system.
 2. A vehicularradio communications system as claimed in claim 1, wherein at least tworadio antennas in said set of external radio antennas; the at least tworadio antennas are in a set of internal radio antennas; and saidplurality of radio-frequency interfaces comprises: (i) a third selectedradio-frequency interface comprising a third duplex processor interfaceand a third duplex antenna interface connected respectively to saidprocessor and to a third radio antenna, said third radio antenna beingin said set of external radio antennas; and (ii) a fourth selectedradio-frequency interface comprising a fourth duplex processor interfaceand a fourth duplex antenna interface connected respectively to saidprocessor and to a fourth radio antenna, said fourth radio antenna beingin said set of local radio antennas.
 3. A vehicular radio communicationssystem as claimed in claim 1, wherein each of the selectableradio-frequency interfaces is configured for fixed operation in a singlefrequency band.
 4. A vehicular radio communications system as claimed inclaim 1, wherein each of the radio-frequency interfaces is a tuneablemulti-frequency interface configured for frequency tuneable operation ina plurality of different frequencies bands.
 5. A vehicular radiocommunications system as claimed in claim 4, wherein the control systemis operatively connected to each tuneable multi-frequency interface, andthe control system controls the frequency response of each interface tothe required frequency band of operation.
 6. A vehicular radiocommunications system as claimed in claim 5, wherein each of saidradio-frequency interfaces comprises a frequency adjustment system foradjusting the operational frequency of filters and/or amplifiers of saidinterface and the control system is connected to each of said frequencyadjustment systems and is configured to coordinate the adjustment ofsaid operational frequencies of said of filters and/or amplifiers inaccordance with said changes in said frequency bands to be used.
 7. Avehicular radio communications system as claimed in claim 5, wherein thecontrol system changes the frequency response of a receiver amplifierand/or the transmitter amplifier within the radio-frequency interface tomatch said changes in the network frequency band of operation.
 8. Avehicular radio communications system as claimed in claim 5, wherein thecontrol system is operable, in use, to change the frequency response ofat least one frequency filter circuit selectably linkable to thereceiver amplifier and/or at least one selectable frequency filtercircuit selectably linkable to the transmitter amplifier, the controlsystem being operable, in use, to select which of said frequency filtercircuits is linked to said amplifiers in order to change said frequencyresponse of the receiver amplifier and/or the transmitter amplifier. 9.A vehicular radio communications system as claimed in claim 1, whereineach radio-frequency interface comprises between the duplex processorinterface and the duplex antenna interface a transceiver system, thetransceiver system comprising a transceiver amplifier circuit, saidcircuit comprising a receive path and a transmit path, the receive pathincluding a receiver amplifier being configured to amplify a downlinkradio signal received from the duplex antenna interface and to providesaid amplified signal to the duplex processor interface, and thetransmit path including a transmitter amplifier being configured toamplify an uplink radio signal received from the duplex antennainterface and to provide said amplified signal to the duplex antennainterface.
 10. A vehicular radio communications system as claimed inclaim 1, wherein the switching system comprises, between said radiofrequency interfaces and the bi-directional processor, a processormultiplexer.
 11. A vehicular radio communications system as claimed inclaim 1, wherein the processor multiplexer is connected to the duplexprocessor interface.
 12. A vehicular radio communications system asclaimed in claim 10, wherein the processor multiplexer is connected to acoder/decoder interface of the bi-directional processor.
 13. A vehicularradio communications system as claimed in claim 10, wherein theswitching system comprises, between said radio frequency interfaces andthe sets of antennas, an antenna multiplexer.